1. Field of the Invention
This invention relates to a mechanism for operating a series of isolation switches that are integral components of bypass isolation switches.
2. Background Information
In many installations it is common to have an alternate AC power source in the event that commercial power is lost or becomes unreliable. Such an alternate power source often comprises for instance an AC generator driven by an internal combustion engine. For switching between sources a transfer switch disconnects one power source and connects the other.
Typically a transfer switch is comprised of two circuit interrupting devices, such as two circuit breakers or two molded case switches or one of each. One switch or breaker is used for the normal power source and the second switch or breaker is used for the emergency power source. In this arrangement one circuit interrupting device is always in the OFF position when the second circuit interrupting device is in the 0N position. Typically, the two circuit interrupting devices have a handle which is used to change the circuit interrupting device from an OFF position to an ON position and may operate through a RESET position.
The art has connected the two circuit interrupting devices together for simultaneous, mutually opposing operation in two ways. First, a bar has been placed between the handles which either pivots around a central point or moves along a longitudinal axis through the circuit interrupting devices. The bar arrangement provides no mechanical advantage and thus is not practical for gang operation of three or more large circuit interrupting devices. That is so because the handles on such large circuit interrupting devices are spring biased with a stiff spring. Second, a three gear mechanism which is manually operated or powered by an unidirectional motor has been used to activate two circuit interrupting devices in a transfer switch. The center gear drives two outer spur gears. Nylon rollers are mounted eccentrically on each of the outer spur gears, which drives an associated cam. The cams travel vertically on guide rods attached to the mechanism's housing. Each cam engages a handle of a circuit interrupting device. In this mechanism the gears can rotate 360.degree. and the cams will move in opposite directions relative to one another. This mechanism can provide a mechanical advantage. However, because of the arrangement of gears it is not able to turn both circuit interrupting devices to the same position, i.e., both OFF or both ON.
Many systems also include a bypass isolation switch in addition to a transfer switch. A bypass isolation switch is used to first completely isolate the transfer switch from both power sources as well as from the load. Secondly, after isolating the transfer switch the attendant power source is reconnected to load through the appropriate bypass switch. Now the transfer switch may be safely removed for routine maintenance.
An isolation switch is typically comprised of three circuit interrupting devices that may be gang operated in order to simultaneously isolate the transfer switch from the normal power supply, emergency power supply and the load. A key lock can be provided such that the key is captive until the isolation switch is locked in the isolated position. Once the isolation switch is locked in the isolated position the key may be removed to unlock the appropriate bypass switch.
A bypass switch is typically comprised of two circuit interrupting devices that are of the same type of unit as is used in the respective transfer switch circuit interrupting device. One device is provided for bypassing to the normal power source and the other for bypassing to the emergency power source. Each circuit interrupting device is provided with a key lock such that only one of the bypass circuit interrupting devices may be unlocked and turned to the ON position by using the key from the locked isolation switch. The key is captive in this lock and may be not removed until the bypass switch is turned to the OFF position and locked.
The commercially available circuit interruption devices which are used as isolation switches have three positions: ON, OFF and RESET. When the circuit interruption device is in an ON position and a short circuit or other electrical failure occurs to automatically open the circuit interruption devices, the device will automatically go to an intermediate position between the ON position and the OFF position. To reactivate the switch one must push the handle to a RESET position and then return it to an ON position. In most circuit interruption devices the OFF position of the handle is located between the ON position and the RESET position. If the handle is held in an ON position when an automatic opening occurs the device will still disconnect. Holding the switch handle in an ON position will not prevent the circuit interruption devices from automatically opening. Westinghouse molded case circuit interruption devices are commonly used in these switching applications. It requires some force to move the handle of the Westinghouse circuit interruption devices and other commercially available alternative circuit interruption devices from an ON position, to an OFF position to a RESET position. If one were to interconnect the handles of three such circuit interruption devices with a bar, it would require considerable force to activate all three circuit interruption devices simultaneously. Indeed, most workmen would be unable to move all three switches together or find that task to be very difficult. Consequently, there is a need for an isolating mechanism that can be easily operated by an average person to simultaneously move the levers of three circuit interruption devices in an isolation switch from an 0N position, to an OFF, to a RESET position.